The Animal Metabolic Physiology Core is designed to meet the needs for characterization of rodent models that have alterations in glucose homeostasis, insulin action, leptin action and/or body composition. Its main function is to teach and provide consultation on ex vivo and in vivo methods to investigate the mechanisms for metabolic alterations in genetically-manipulated mouse models and in dietary models of obesity/leanness or insulin resistance/sensitivity. The specific objectives of the Core are 1) to teach and 2) to provide consultation to investigators in designing, carrying out and interpreting in vitro and in vivo studies to investigate the action of insulin and hormones that regulate energy balance such as leptin; glucose homeostasis; lipid metabolism; and body composition; 3) The Core also performs a limited number of these studies on selected mouse or rat models created by or obtained by members of the Center. Services of the Core include ex vivo methods such as adipocyte isolation, and dissection and incubation of isolated skeletal muscles to study glucose transport, insulin signaling, leptin signaling, and glucose and fatty acid metabolism. In vivo methods assessing insulin action and glucose homeostasis include insulin tolerance test, glucose tolerance test, signaling assays in response to insulin injection or infusion, and measurement of glucose turnover, endogenous glucose production and glucose uptake by individual tissues during clamp studies. In vivo methods to investigate biological actions of orexigenic and anorexigenic hormones include measurement of food intake, energy expenditure and leptin signaling in peripheral tissues and hypothalamic nuclei. The Core also provides specialized equipment such as a DEXA scanner for non-invasive analysis of body composition and bone mineral density and a Coulter Counter for determining adipocyte number and size distribution. The Core Director, Barbara B. Kahn, MD, the Associate Core Director, Odile Peroni, PhD and the Research Associates who work with the Core have extensive experience with the metabolic and signaling assays offered by the Core. They are developing new assays to characterize additional aspects of integrated fuel metabolism and enerov homeostasis.